Transformer module for a welder

ABSTRACT

An electric arc welder comprising a high switching frequency inverter for driving the primary of an output transformer where the output transformer has a plurality of modules forming the secondary windings of the transformer and each of the modules comprises a first coaxial set of concentric, telescoped tubes separated by a tubular insulator, a second coaxial set of concentric, telescoped conductive tubes separated by a tubular insulator wherein the sets each have an elongated central passage for accommodating the primary and a conductor connecting the tubes into a series circuit. These modules form a transformer for such welder.

The present invention relates to the art of electric arc welding andmore particularly to a modular transformer operated by high frequencyand having an output for welding and a module for such transformer.

INCORPORATION BY REFERENCE

The invention relates to a module that can stand alone or be combinedwith similar modules to form a high frequency transformer for use inelectric arc welding. The actual electrical circuit for the transformercan vary; however, a representative transformer circuit is shown inBlankenship U.S. Pat. No. 5,351,175 incorporated by reference herein asbackground information. The transformer module is an assembly whichforms the secondary of a transformer, wherein the primary is interleavedthrough one or more modules. If more than one module is used, they areused in a matrix transformer. This technology is well known and is shownin Herbert U.S. Pat. No. 4,942,353 which is incorporated herein so thatdisclosure of the matrix transformer technology need not be repeated. InHerbert U.S. Pat. No. 5,999,078 two adjacent magnetic cores are providedwith secondary windings and primary windings wherein each moduleincludes a half turn of the secondary winding. These modules merelyprovide a flat conductive strip through a core to be connected as a partof a secondary winding. The primary winding is then interleaved throughthe modules in accordance with standard matrix transformer technology. Asimilar module having several turns in a given core is shown in Herbertpublication No. 2002/0075119. This patent and publication areincorporated herein to show prior art technology regarding a module usedfor a secondary winding in a matrix type transformer. All of thesepatents are included as background information.

BACKGROUND OF INVENTION

In electric arc welding it is necessary to create high currents from apower source, such as an inverter. To accomplish this objective, theinverter must be operated at a switching frequency which is quite high,such as 40 kHz so that the size of the components and the cost of thecomponents are low. To create high currents from power sources usinghigh switching frequencies, it is normal to merely employ an outputtransformer involving a primary and secondary. Consequently, thetransformer has to be relatively robust in construction and capable ofgenerating and handling high currents. Such transformers are quiteexpensive and bulky.

THE INVENTION

The present invention relates to electric arc welding wherein a powersource is operated at high switching frequency, such as 40 kHz. Inaccordance with the invention, the output transformer of this electricarc welder is a coax configuration where the secondary windings of theoutput transformer are constructed so the primary winding can be passedthrough one or more module to produce a highly coupled transformer witha very compact construction and enhanced heat dissipationcharacteristics. The invention is directed to a novel and unique moduleconstruction allowing a single module or multiple modules to be appliedto an electric arc welder. A single or multiple modules are useddependent on the power output requirements.

The module of the present invention comprises a first coaxial set ofconcentric, telescoped conductive tubes separated by a tubularinsulator, a second coaxial set of concentric telescoped conductivetubes separated by a tubular insulator and a magnetic core around eachof the tube sets so that each set of conductive tubes has an elongatedcentral passage for accommodating at least one primary winding. Thismodule includes a conductor connecting the tubes of the sets into aseries circuit so the output of each module is directed to a rectifierfor conversion into a portion of the output current necessary forelectric arc welding. The current from all of the modules are summed toobtain a welding current.

By using this unique module design, the module can be used by itself oras a plurality of modules can be interleaved with one or more primariesto create a welding current having an output capability in excess of1000 amperes.

The primary object of the present invention is the provision of amodular transformer for an electric arc welder.

A further object of the present invention is the provision of a module,as defined above, which module involves parallel coaxial tubes connectedin series and defining central passages for a primary or primaries ofthe output transformer of a power source used in electric arc welding.

Yet another object of the present invention is the provision of amodule, as defined above, which module employs two concentric conductivetubes connected in series in a single module to define a multi-turnsecondary winding for an output transformer of an electric arc welder.

A further object of the present invention is the provision of a matrixtransformer at the output of a power source used in electric arcwelding.

These and other objects and advantages will become apparent from thefollowing description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a pictorial view of a module constructed in accordance withthe present invention;

FIG. 2 is a side elevational view of the module showing in partialcross-section one side of the concentric tube construction;

FIG. 3 is a schematic wiring diagram illustrating the current flow in amodule as shown in FIGS. 1 and 2;

FIG. 4 is a wiring diagram of the module shown in FIGS. 1-3 inconjunction with a single primary winding interleaved through thepassages of the parallel concentric tube module;

FIG. 5 is a schematic wiring diagram similar to FIG. 3 illustrating amodified module utilizing two parallel tubes with a full wave outputrectifier;

FIG. 6 is a wiring diagram showing three modules as illustrated in FIGS.1-3 connected as the output of the power transformer in an electric arcwelder;

FIG. 7 is a schematic wiring diagram of the high switching speedinverter used for the primary winding and/or windings that areinterleaved in the modules schematically represented in FIG. 6 and shownin detail in FIGS. 1-3 and in FIG. 8; and,

FIG. 8 is a pictorial view of three modules connected as shown in FIG. 6utilizing a plurality of modules as disclosed in FIGS. 1-3.

PREFERRED EMBODIMENT

A novel secondary module constitutes the basic building block of thepresent invention. The preferred embodiment is shown in FIGS. 1 and 2wherein secondary module A is constructed to receive one or more primarywindings P through a pair of parallel cylindrical openings designed toaccommodate one or more primary windings in parallel relationship.Module A is used both as a single secondary winding, or as one ofseveral modules in a matrix transformer where primary winding P isinterleaved through two or more modules A as will be explained later. Inthe preferred embodiment, module A is formed from a first assembly 10with a first tube 12 terminating in a lower tab 14 having a connectorhole 16. Central passage 18 in tube 12 is used as the primary windingpassage when module A includes only the first assembly 10. As will beexplained, the preferred embodiment has two assemblies formed bytelescoping two coaxial conductive tubes usually formed from copper andtelescoped around each other. Second tube 20 of first assembly 10includes a terminal tab 22 with a lower connector hole 24 and has acentral cylindrical passage 26. To fix tube 12 with respect to tube 20,so the tubes are in parallel and in spaced relationship, a first jumperstrap 30 is provided. Two space holes in strap 30 surround the first endof tubes 10, 20 so weld joints 32 fix the tubes into the holes. As sofar described, the jumper strap is at one end of the tubes and the tubesare parallel and spaced with the second ends having protruding tabs 16,22, respectively. As will be explained later, only assembly 10 may beused; however, the preferred embodiment involves a coaxial relationshipinvolving a second assembly 40 essentially the same as assembly 10 withtubes having lesser diameter so that they telescope into tubes 12, 20.Assembly 40 includes third tube 42 having a lower tab 44 with aconnector hole 46 and a central passage 48 to accommodate winding P. Afourth tube 50 has a lower tab 52 with a connector hole 54 so that thethird and fourth tube can be joined by a second jumper strap 60 providedwith spaced openings surrounding the top or first end of tubes 42, 50.Weld joint 62 around the tubes joins the tubes into the holes of jumperstrap 60. This second assembly is quite similar to the first assemblyexcept the diameters of tubes 42, 50 are substantially less than thediameters of tubes 12, 20. In the cylindrical gap between the tubes, aNomex insulator sleeve or cylinder 70, 72 is provided. These cylindricalinsulator sleeves electrically isolate the coaxial tubes forming thebasic components of module A. Plastic end caps 80, 82 are provided withtwo transversely spaced recesses 84 in cap 80 and two spaced recesses 86in cap 82. Only one of the recesses 84, 86 is illustrated in FIG. 2. Theother recesses are the same and need not be illustrated. Theconstruction of the left coaxial assembly of module A is essentially thesame as the construction of the right coaxial assembly as shown incross-section in FIG. 2. As illustrated, between cap recesses 84, 86there are provided a plurality of ferrite donut-shaped rings or magneticcores 90-98. To center the cores there are provided a number of siliconwashers 100 so bolts 110 having heads 112 clamp the end caps together.This action holds the spaced rings around the coaxial tubes of module A.Assemblies 10, 40 with the coaxial tubes are held onto module A by anupper plastic nose 120 having an arcuate primary winding guide 122. Thenose is held onto end plate 82 by transversely spaced bolts 124. Nose120 includes laterally spaced slots 126, 128 so that the nose can bemoved from one edge of assemblies 10, 40 to the center position byriding on spaced jumper straps 30, 60. When in the center of the module,the plastic nose is bolted to end cap 82. This clamps assemblies 10, 40onto module A in the position shown in FIG. 2 and holds straps 30, 60 inspaced relationship. The coaxial tubes are aligned by holes 80 a, 82 aconcentric with cylindrical recesses 84, 86 in end caps 80, 82,respectively. Two of these holes are located in each of the end caps.Washers 100 center the coaxial tubes in the cylinder formed by corerings 90-98.

In the preferred embodiments, module A is connected as a secondary for ahigh frequency transformer driven by a primary from an inverter. Thiselectrical arrangement involves connecting assemblies 10, 40 in seriesby a center tap connector 130 having holes 132, 134 and 136. A rivet 140connects hole 132 with tab 52, while rivet 142 connects hole 136 withtab 14. To stabilize center tap 130, the ends of the tap are providedwith cylindrical wings 144, 146, best shown in FIG. 2. As shown in FIG.3, module A is connected to rectifier 150 having diodes 152, 154 and anoutput terminal 156. By this arrangement, the single coaxial moduleallows primary winding or windings P to be leaved through cylindricalpassages 48, 56 so the module is a secondary of a high frequencytransformer. This is a normal use of the present invention when employedfor an electric arc welder. A simplified wiring diagram of theembodiment is illustrated in FIG. 4 to show primary winding P andsecondary windings 12/20 and 42/50.

In accordance with an aspect of the invention, module A′ shown in FIG. 5includes only tube assembly 10 with only conductive tubes 12, 20 thatdefine terminal ends 16, 24. These terminals are connected across a fullwave rectifier 160 having output terminals 162, 164. Tubes 12, 20 couldbe a single tube; however, in the invention two tubes are used tominimize inductance so the primary winding from the inverter is leavedaround jumper 30 through center winding accommodating openings 18, 26.

A plurality of modules A are arranged to provide a high frequencytransformer for a welder represented by electrode E and workpiece W inFIG. 6. This matrix transformer concept is illustrated schematically inFIGS. 6-8 wherein modules A1, A2 and A3 are joined together by endstraps 190, 192 in one end of the multiple module assembly shown in FIG.8 and end straps 194, 196 on the other end. Bolts clamp a frame aroundmodules A1, A2 and A3 to assemble them into alignment, as shown in FIG.8 wherein each set of passages 48, 56 is in parallel and are aligned inside-by-side relationship. The wiring diagram for the assembly shown inFIG. 8 is illustrated in FIG. 6 wherein terminals 156 are connected inparallel at terminal 170 and center tap 148 is connected in parallel atterminal 172. The primary windings from one or more inverters are shownschematically in the wiring diagram of FIG. 7. Inverter 200 creates anAC current in primary P1. In a like manner, inverter 202 provides an ACcurrent in primary P2. These two primaries are interleaved togetherthrough modules A1, A2 and A3. In practice, two primary windings areused in the matrix transformer of FIG. 8; however, a single winding isalso used in this type of matrix transformer. FIGS. 6-8 merelyillustrate that the coaxial secondary transformer module A of FIGS. 1-3can either be used as a single secondary winding or as parallelsecondary windings in a matrix transformer. Other arrangements usemodule A as a secondary winding for a transformer between an inverterand a welding operation. The tubular, coaxial conductors disclosed inmodule A are sometimes replaced by an elongated ribbon helix around thecenter axis of the individual tubes. Such helix configuration stillprovides the coaxial relationship between the concentric tubes. The term“tube” defines a continuous tube conductor, as so far described, or thehelix tube as used in the alternative embodiment.

1. (canceled)
 2. The high speed frequency transformer of claim 36wherein each of said magnetic cores comprises a plurality ofdoughnut-shaped rings around one of said tubes. 3-4. (canceled)
 5. Thehigh frequency transformer of claim 36 wherein each of said first andsecond modules further includes a conductive assembly comprising a thirdconductive tube with first and second ends, a fourth conductive tubewith first and second ends and a second jumper strap joining said firstends of said third and fourth tubes into a parallel relationship to eachother and to said first and second tubes; said third and fourth paralleltubes being telescoped into said passages of said first and secondtubes, respectively, and having elongated passages for accommodatingsaid primary winding or windings with said first and second jumper strapspaced from each other; a first tubular insulator between said first andthird tubes; a second tubular insulator between said second and fourthtubes; and a center tap connector joining said conductive assembly to asecond end of one of said first and second tubes to form said tubes intoa series circuit.
 6. A module as defined in claim 5 wherein said secondend of one of said first and second tubes and one end of one of saidthird and fourth tubes are connected to a rectifier. 7-21. (canceled)22. An electric arc welder comprising an output transformer and a highswitching frequency inverter for driving the primary of the outputtransformer, said output transformer having a plurality of modulesforming secondary windings, each of said modules comprising a firstcoaxial set of concentric, telescoped tubes separated by a tubularinsulator, a second coaxial set of concentric, telescoped conductivetubes separated by a tubular insulator, said sets each accommodatingsaid primary, and a conductor connecting said tubes into a seriescircuit.
 23. A welder as defined in claim 22 wherein said tubes of saidmodules are each connected to a rectifier to create a positive andnegative current output and a circuit connecting said outputs inparallel.
 24. (canceled)
 25. A power source as defined in claim 44wherein said tubes of said modules are each connected to a rectifier tocreate a positive and negative current output and a circuit connectingsaid outputs in parallel.
 26. A power source as defined in claim 25wherein said tubes of said modules are formed by an elongated ribbonhelixed around a central axis of said tube. 27-34. (canceled)
 35. A highfrequency transformer of an electric arc welder, comprising: a firstmodule having a first module secondary winding section; a second modulehaving a second module secondary winding section, said first modulesecondary winding section interconnected with said second modulesecondary winding section; and a primary winding through each of saidfirst and second modules.
 36. The high frequency transformer of claim 35wherein each of said first and second modules includes: a firstconductive tube with first and second ends and a central elongatedpassage; a generally parallel second conductive tube with first andsecond ends and a central elongated passage; and a magnetic coresurrounding each of said first and second tubes, wherein said primarywinding is accommodated in said central elongated passages of said firstand second tubes, said first ends of said tubes are joined together by ajumper strap, and a circuit forming connector is disposed at said secondends of said tubes.
 37. The high frequency transformer of claim 35further including a third module having a third module secondary windingsection, said winding sections of said first, second and third modulesinterconnected and said primary winding through each of said first,second and third modules.
 38. The high frequency transformer of claim 35wherein each of said modules has a given current capacity and a totaloutput welding current is the sum of the given current capacities ofeach of said first and second modules.
 39. The high frequencytransformer of claim 38 wherein said total output exceeds about 1,000amperes.
 40. The high frequency transformer of claim 38 wherein thegiven current capacity of each of said first and second modules isapproximately the same.
 41. The high frequency transformer of claim 35wherein said first and second modules are readily removable from oneanother.
 42. The high frequency transformer of claim 35 wherein theprimary is driven by a high frequency inverter.
 43. The welder of claim22 wherein said sets of tubes each have an elongated passageaccommodating said primary.
 44. The welder of claim 22 wherein each ofsaid plurality of modules is readily removable from said outputtransformer.
 45. A power source for electric arc welding, said powersource includes a high switching speed inverter for driving the primaryof an output transformer with AC primary current, said outputtransformer having a number of modules each with a given currentcapacity forming the secondary winding of the output transformer, saidmodules connected in parallel with the total output welding currentbeing the sum of the current capacities of said separate modules andable to exceed about 1,000 amperes.
 46. A power source as defined inclaim 45 wherein said given current capacities are the same.
 47. A powersource as defined in claim 45 wherein each of said number of modulescomprises a first conductive tube with first and second ends; agenerally parallel closely adjacent second conductive tube with firstand second ends, said tubes each having a central elongated passageaccommodating one or more primary windings; a magnetic core surroundingeach of said tubes; a jumper strap joining said first ends of saidtubes; and, a circuit forming connector at said second ends of saidtubes.
 48. A power source as defined in claim 47 wherein each of saidnumber of modules includes a conductive assembly comprising a thirdconductive tube with first and second ends, a fourth conductive tubewith first and second ends and a second jumper strap joining said firstends of said third and fourth tubes into a parallel relationship to eachother and to said first and second tubes; said third and fourth paralleltubes being telescoped into said passages of said first and secondtubes, respectively, and having elongated passages accommodating saidprimary winding or windings with said first and second jumper strapspaced from each other; a first tubular insulator between said first andthird tubes; a second tubular insulator between said second and fourthtubes; and a center tap connector joining said conductive assembly to asecond end of one of said first and second tubes to form said tubes intoa series circuit.